Device and method for radiation therapy

ABSTRACT

There is provided a device and a method for irradiating vascular tissues. The device generally includes a transfer device having a first chamber and a second chamber and a piston slidably disposed between the chambers. A ballon catheter is provided for positioning witin the vascular system and is connected to the transfer device such that an inflation lumen of the balloon catheter is in fluid communication with the second chamber. A proximal end of the balloon catheter is affixed to a mounting block which is configured to receive the transfer device. An inflation device is provided to force fluid into the first chamber such that the piston is driven to force a radioactive fluid contained in the second chamber into the balloon.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 60/071,342 filed on Jan. 14, 1998, entitled “Device and Method forRadiation Therapy, ” the entire contents of which are incorporatedherein by reference and also Ser. No. 60/077,294 filed Mar. 6, 1998, anda continuation of Ser. No. 09/073,932 filed May 6, 1998 now U.S. Pat.No. 5,961,439.

TECHNICAL FIELD

The technical field relates generally to the use of radiation therapyafter an angioplasty procedure, to minimize the occurrence of restenosisand, more particularly, to a device and method for delivering a radioisotope to a stenotic region, e.g., in liquid or gaseous form, toinhibit restenosis.

DESCRIPTION OF THE RELATED ART

A common treatment for blockage or stenosis of the arteries is aprocedure known as percutaneous transluminal angioplasty (PTA) and, whenutilized within the coronary artery, is known as percutaneoustransluminal coronary angioplasty (PTCA). During this procedure, thelocation of a stenotic constriction or blockage within the coronaryartery is identified and a guide wire is advanced through the vascularsystem to a point distal to or beyond the blockage. Subsequently, anangioplasty catheter in one form having an inflatable angioplastydilatation balloon at a distal end thereof or in a second form anatherectomy catheter, or a stent delivery catheter, is advanced alongthe guide wire until the balloon is located at the point ofconstriction. The balloon is then repeatedly inflated and deflated toopen the constriction by compressing the plaque against the vesselwalls. In this manner, a constriction within the vascular system may beopened to allow increased blood flow. Similarly, the plaque can beremoved by atherectomy, or the plaque can be scaffolded by placing astent.

The vascular tissue may respond to the trauma by proliferative growth ofcells responsible for restenosis, e.g., smooth muscle tissue cells,deposition of extracellular matrix material. Upon increased growth ofsuch cells, the formerly constricted area may become reconstricted ornarrowed down, which is commonly referred to as “restenosis.” This canoccur any time from within a few weeks to several years following theoriginal angioplasty procedure, thus, often necessitating repeatedangioplasty procedures to reopen the constriction. Other causes ofrestenosis have been reported including, but not limited to, elasticrecoil of the vessel wall and focal shrinkage of the vessel wall,commonly referred to as “negative remodelling.”

It has been found that by exposing the vascular tissues to radiationsubsequent to the balloon angioplasty procedure, the proliferativegrowth of the smooth muscle cells and/or vessel shrinkage responsiblefor restenosis is inhibited. However, difficulty in providing uniformradiation to the surrounding tissue may arise. Often, after expansion ofa constricted area by a balloon angioplasty procedure, the resultingrelatively unconstricted area has a generally asymmetricalcross-section. The asymmetrical cross-section may pose problems forthose devices which are configured to position a radioactive sourcesubstantially at the center of the vascular structure. Thus, it would bedesirable to have a device and method for delivering a radioactive dosein a substantially uniform manner to the site of a vascular constrictionpost-angioplasty.

SUMMARY

There is provided a device and a method of irradiating vascular tissueswhich have been subjected to a balloon angioplasty procedure. The devicegenerally includes a balloon catheter having an expandable balloon whichcan be positioned over a guide wire within the vascular tissue, atransfer device for transferring radioactive material, e.g., fluid, fromthe transfer device to the balloon and an inflation device for forcingthe radioactive fluid out of the transfer device and into the balloon.The balloon catheter includes an inflation lumen extending from aninterior of the balloon through the catheter to a proximal portion ofthe catheter. The balloon catheter also includes a guide wire lumen. Theguide wire lumen may extend the entire length of the catheter from itsdistal to its proximal end or may extend from the distal end to a pointjust proximal of the balloon. The transfer device includes first andsecond chambers which are separated by a movable piston or membrane. Thefirst chamber is configured to receive a fluid to move the piston withinthe transfer device while the second chamber is configured to receive,retain and shield or isolate the radioactive fluid prior to injectioninto the balloon catheter. The inflation device provides a fluid,preferably saline, to the first chamber to move the piston by creating apositive or negative gauge pressure in the first chamber. Preferably,The inflation device may include a pressure gauge as well as anoverpressure relief valve. As used herein, the term “radioactive fluid”is intended to encompass liquids, gases, solids and/or combinationsthereof.

A mounting block may also be provided to connect the second chamber ofthe transfer device to the inflation lumen of the balloon catheter.Specifically, the mounting block retains the proximal end of the ballooncatheter with the inflation lumen in fluid communication with the secondisotope containing chamber in the mounting block. The mounting blockincludes an injection port having a self-sealing septum which is influid communication with the second isotope containing chamber.

In one embodiment, the mounting block is interlocked to the proximal endof the balloon catheter by use of a bayonet style fitting. It is furthercontemplated that other interlocking optical, mechanical and/orelectrical features and/or structures may be provided, and may includerecognition features to ensure that only a catheter suitable forradiation therapy is coupled to the transfer device. Moreover, suchrecognition features and/or structures may provide information to anassociated system to identify to the system characteristics of thecatheter, e.g., catheter length and size, capacity, etc., which may beused in controlling the transfer device to assure transfer of anappropriate quantity of isotope containing material to the ballooncatheter. The system may calculate, display and/or control treatmenttime and dose delivery and may monitor system integrity, e.g., usingfluid pressure sensors in the catheter, second chamber or mountingblock.

The transfer device includes an injection needle which extends from thesecond chamber and is provided to pierce self-sealing septum in order todraw and inject the radioactive fluid through the self-sealing septum.Preferably, the injection needle is provided with an elastomeric bootsurrounding the needle which acts as a seal against the septum. Thetransfer device may also be provided with a needle shield extending fromthe second chamber and surrounding the injection needle. The transferdevice may be connected to the mounting block by suitable means such asa bayonet style mounting fixture.

There may also be provided a separate source or container for theradioactive fluid which also has a self-sealing septum. The source willalso include a bayonet style mounting fixture for affixing to thetransfer device in order to load the transfer device with theradioactive fluid. Additionally, an aspiration syringe may be providedhaving a needle to pierce the septum of the mounting block in order todraw air out of the balloon and inflation lumen of the balloon catheterto create a vacuum therein.

There is also disclosed a method for irradiating vascular tissues whichincludes providing a transfer device having first and second chambersand a piston movably disposed within the chambers, an inflation devicefor moving the piston within the first and second chambers and a ballooncatheter for carrying a radioactive fluid from the second chamber of thetransfer device to a balloon on a distal end of the balloon catheter.The method includes loading radioactive fluid into the second chamber ofthe transfer device, positioning the balloon at a stenotic region withinthe vascular system, attaching the transfer device to a proximal portionof the balloon and attaching an inflation device to the transfer devicesuch that the inflation device can force fluid into the first chamber ofthe transfer device. The method further includes forcing fluid from theinflation device into the transfer device to force the piston to forcethe radioactive fluid out of the second chamber of the transfer deviceand into the balloon to substantially fill the balloon therebyirradiating surrounding tissues with the radioactive fluid. The methodmay further include the step of removing air from the balloon catheterprior to the step of inserting the catheter in the vascular system.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments are described herein with reference to the drawingswherein:

FIG. 1 is a perspective view of a system for providing a fluid radiationtherapy treatment;

FIG. 1A is a perspective view of a radiation fluid source container;

FIG. 1B is an enlarged perspective view of the distal end of a treatmentcatheter associated with the system of FIG. 1;

FIG. 1C is a perspective view, partially shown in section, of a transferdevice associated with the system of FIG. 1;

FIG. 1D is an enlarged view of a booted needle of the transfer device ofFIG. 1C;

FIG. 2 is a perspective view of the transfer device and radiation fluidsource container;

FIG. 2A is a side elevational view, partially shown in section,illustrating the assembled inflation device, transfer device andradiation fluid source container of the system of FIG. 1;

FIG. 2B is an enlarged side view, shown in section, illustratingengagement of the transfer device with the fluid source container;

FIG. 2C is an enlarged view illustrating engagement of the inflationdevice with the transfer device as well as a pressure relief valveassociated with the inflation device;

FIG. 3 is a side view, partially shown in section, of the ballooncatheter, mounting block and aspiration syringe of FIG. 1;

FIG. 3A is an enlarged sectional view of the distal end of the ballooncatheter of FIG. 3;

FIG. 3B is an enlarged view of the distal end of the mounting blockassociated with the catheter of FIG. 3;

FIG. 3C is an enlarged view of the proximal end of the mounting blockassociated with the catheter of FIG. 3;

FIG. 4 is a side view, shown in section, of the distal end of theballoon catheter of FIG. 1, inserted into a vascular system over a guidewire and positioned at a location of an expanded stenotic region;

FIG. 5 is a perspective view of the transfer device being moved intoengagement with the mounting block;

FIG. 6 is an enlarged perspective view of the device for radiationtherapy of FIG. 1 with the balloon catheter inserted into a patient;

FIG. 7 is a side elevational view, partially shown in section, of theassembled inflation device, transfer device and mounting block;

FIG. 7A is an enlarged view illustrating injection of radioactive fluidfrom the transfer device-to the mounting block;

FIG. 8 is a side view, shown in section, illustrating expansion of theballoon at the distal end of the catheter by the radioactive fluid andinto contact with the surrounding tissue;

FIG. 9 is an enlarged view of the pressure relief valve associated withthe inflation device in operation;

FIG. 10 is an elevational cross-section view of a rapid exchange stylecatheter for use with the system of FIG. 1; and

FIG. 10A is an enlarged view of the distal end of the balloon catheterof FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, there is disclosed a preferred embodiment of asystem 10 for radiation therapy. System 10 is particularly configured todeliver a source of radioactive fluid to a treatment balloon which hasbeen positioned within a vascular system at the site of a previousangioplasty procedure. System 10 generally includes a device forradiation therapy 12, a container such as a vial or other source ofradioactive fluid 14, and an aspiration syringe 16. Device for radiationtherapy 12 includes a balloon catheter 18 which extends from a mountingblock 20. A transfer device 22 is removably engagable with mountingblock 20. There is also provided an inflation device 24 which isremovably engagable with transfer device 22. Inflation device 24 isprovided to force radioactive fluid out of transfer device 22 andthrough mounting block 20 into balloon catheter 18. Preferably, apressure relief valve 26 may be positioned between inflation device 24and transfer device 22 to prevent over expansion of balloon catheter 18.

Inflation device 24 is of known type utilized in balloon angioplastyprocedures and may include a pressure gage 28 to monitor the exactpressures. This is particularly preferable in the present radiationtreatment procedure where it is not necessary to reach high pressureswithin the balloon catheter, but rather to merely expand the balloon tothe point that it contacts surrounding tissue and plaque.

In order to connect transfer device 22 to inflation device 24, transferdevice 22 is provided with a flange 30 at a proximal end 32 thereof.Flange 30 is engagable with a threaded coupling 34 associated withinflation device 24. Similarly, to connect transfer device 22 tomounting block 20, transfer device 22 is provided with the male half ofa “bayonet-type” or “luer” fitting 36 at a distal end 38 thereof. Themale half of the bayonet or luer fitting 36 is engagable with a femalehalf of a bayonet or luer fitting 40 positioned on mounting block 20. Asused herein, the term proximal refers to that portion of the devicecloser to the user while the term distal refers to that part of thedevice further from the user. In order to prevent leakage of radioactivefluid during transfer from transfer device 22, mounting block 20 ispreferably provided with a self-sealing elastic septum 42 which is influid communication with balloon catheter 18.

To facilitate loading of the radioactive fluid into transfer device 22,20 source 14 also includes a female half of a bayonet or luer fitting 44which is engagable with the male half of the bayonet or luer fitting 36on transfer device 22. Additionally, source 14 also includes aself-sealing elastic septum 46 to prevent inadvertent leakage ofradioactive fluid.

Referring now to FIG. 1A, it can be seen that the bayonet style fitting44 on source 14 is of known variety including a plurality of L-shapedslots 48 formed within a circumferential flange 50. It is contemplatedthat other locking structures such as, e.g., luer locks, may besubstituted for the bayonet-style fitting 44. Self-sealing septum 46projects a predetermined distance above flange 50. Referring for themoment to FIG. 1B, it can be seen that a distal end 52 of ballooncatheter 18 generally includes an elastomeric sleeve or balloon 54mounted on a catheter shaft 56. Balloon catheter 18 may be configured aseither an over the wire (OTW) type catheter or a rapid exchange “RE”catheter. When an OTW style catheter is used with device 12 forradiation therapy, a guide wire lumen 58 extends generally throughoutthe length thereof for receipt of a guide wire 126 as describedhereinbelow.

Referring now to FIG. 1C, it can be seen that transfer device 22includes an enlarged saline housing 60 and a radioactive fluid housing62 extending from extended large saline housing 60. A needle shield 64extends distally from radioactive fluid housing 62 and is provided witha plurality of projections 66 which form the male half of the bayonetfitting 36 on distal end 38 of transfer device 22. As noted above,flange 30 is provided at proximal end 32 of transfer device 22 forengagement with inflation device 24. In order to transfer radioactivefluid between transfer device 22 and self-sealing septum 42 of mountingblock 20 or self-sealing septum 46 of source 14, transfer device 22 isprovided with a booted needle 68 provided within needle shield 64.Booted needle 68 extends distally from radioactive fluid housing 62.Referring for the moment to FIG. 1D, booted needle 68 generally includesan inner needle 70 having a sharply pointed tip 72 which is configuredto pierce elastomeric self-sealing septums 42 and 46. Needle 70 may beformed of any suitable material, for example, stainless steel. Bootedneedle 68 further includes an elastomeric sleeve or boot 74 whichsurrounds needle 70. Boot 74 is provided to further shield pointed tip72 of needle 70 and to serve as a further seal against a septum toprevent inadvertent release of radioactive fluid when fluid is beingdrawn into or forced out of needle 70 or when the system isdisconnected.

Referring to FIG. 2, in order to load the radioactive fluid from source14 into transfer device 22, transfer device 22 is positioned such thatmale bayonet 36 at the distal end 38 thereof is brought into engagementwith the female bayonet fitting 44 on source 14. As transfer device 22is brought into engagement with source 14, booted needle 70 (FIG. 1D) isbrought into engagement with and pierces self-sealing septum 46.

Referring now to FIG. 2B, the construction of transfer device 22 willnow be described. Enlarged saline housing 60 defines an internal salinechamber 76 for receipt of saline fluid S from inflation device 24.Similarly, radioactive fluid housing 62 defines an interior isotopechamber 78 for receipt of the radioactive fluid or isotope I from source14. The isotope I is stored in isotope chamber 78 until it is forced outinto balloon catheter 18 during use. In order to move the isotope fluidI out of or into isotope chamber 78, there is provided a piston 80movably positioned within chambers 76 and 78. Piston 80 includes anenlarged piston head 82 positioned within saline chamber 76 and asmaller piston head 84 which is movably positioned within isotopechamber 78. A piston shaft 86 connects piston heads 82 and 84. It shouldbe noted that the particular dimensions of piston head 82 and pistonhead 84 may be varied in order to produce desired magnification orreduction of relative fluid pressure between saline fluids in salinechamber 76 and isotope fluid I in isotope chamber 78. Also it should benoted that if saline chamber 76 and isotone chamber 78 are of the samediameter then piston heads 82 and 84 can be replaced with a singlepiston.

Referring further to FIG. 2B, it can be seen that source 14 defines aninternal isotope chamber 78 which contains a quantity of radio activeisotope I. Radio active isotope I is a beta or gamma emitting radioisotope and is preferably 50-100 millicuries of RE 188 which may beeasily generated at hospitals and is readily available. A preferredradio active isotope is thus provided in liquid form and generally has arelatively short half life. However, safety precautions need bemaintained to prevent contamination of the interventional cardiologylaboratory. As shown, when needle shield 64 is engaged with source 14,needle 70 is forced through self-sealing septums of boot 74 and septum46. Self-sealing septum 46 provides a fluid tight seal about needle 70.Additionally, elastomeric boot 74 is compressed against elastomericseptum 46 and provides a further seal therebetween. Referring for themoment to FIG. 2B, in order to fill transfer device 22 with isotope I,inflation device 24 is engaged with transfer device 22 in a mannerdescribed hereinabove and is further illustrated in FIG. 2C. Salinechamber 76 is initially completely filled with saline fluid S.Thereafter, transfer device is engaged with source 14 in a mannerdescribed hereinabove such that needle 70 punctures the elastomericseptum 46 and is in contact with isotope 1. At this point, negativepressure is provided by inflation device 24 to draw saline out of salinechamber 76. Upon drawing saline fluid S out of saline chamber 76, piston80 is drawn proximally within transfer device 22 thereby forming avacuum in isotope chamber 78. The vacuum created in isotope chamber 78draws the isotope I from chamber 82 and source 14 into chamber 78 intransfer device 22. Once a predetermined quantity of isotope I has beenreceived within chamber 78 of transfer device 22, transfer device 22 andsource 14 may be rotated to disengage their bayonet fittings. Pullingsource 14 away from transfer device 22 draws needle 70 throughself-sealing septum 46 which thereafter seals about itself preventingany further release of radioactive isotope I from source 14. In thismanner, transfer device 22 is loaded with a predetermined amount ofisotope I. Preferably, this procedure takes place inside a radiationlaboratory. Once transfer device has been loaded with isotope I, it maybe retained within a shielded container or safe for transport to theinterventional cardiology laboratory prior to use.

Referring for the moment to FIG. 2C, and as noted above, inflationdevice 24 is provided with a pressure relief valve 26. Pressure reliefvalve 26 is of known variety and generally includes a seal 88 having ashaft 90 extending therefrom. A spring 92 is provided about shaft 90 andbiases seal 88 into engagement with fluid opening 95 in inflation device24. Spring 92 is of a predetermined resistance such that when the fluidpressure within inflation device 24 exceeds a predetermined amount, seal88 allows fluid to flow from inflation device 24 and out through a draintube 94 thereby relieving any excess pressure within device forradiation therapy 12.

Referring now to FIG. 3, the details of the mounting block 20 andballoon catheter 18 will now be described. As shown, balloon catheter 18extends distally from mounting block 20.

Referring to FIG. 3A, the illustrated balloon catheter 18 is of the overthe wire variety including a catheter shaft 56 defining a guide wirelumen 58 extending completely therethrough. As noted above, a balloon 54is affixed to a distal end 52 of balloon catheter 18 and is mounted oncatheter shaft 56. It should be noted that balloon 54 may be formed froman elastic or inelastic material. The balloon 54 may act solely as ameans to deliver the radiation therapy or it may provide a dilatationfunction within a vascular system. In either case, it as a chamber forradioactive fluid to provide uniform irradiation of the surroundingvascular tissue. Balloon catheter 18 includes a balloon inflation lumen96 formed within catheter shaft 56. Preferably, inflation lumen 96 isconcentric with guide wire lumen 58. A plurality of inflation ports 98provide fluid communication between the inflation lumen 96 and aninterior surface of balloon 54. Inflation lumen 96 extends frominflation ports 98 approximately to a mid-portion 100 (FIG. 3) ofmounting block 20.

As shown in FIG. 3B, catheter 18 is preferably secured to mounting block20 by means of a threaded cap 102 at mid portion 100 which engagesthreads 104 formed in a distal end 106 of mounting block 20. Theparticular balloon catheter 18 illustrated is of a variety specificallyconfigured to engage mounting block 20. However, it is also contemplatedthat standard configuration balloon catheters may be utilized with thepresent system requiring only minor modifications, as will be readilyapparent to those skilled in the art, to the utilized catheter andmounting block 20. A circular seal or “O” ring 108 is provided betweenthreaded cap 102 and mounting block 20 to provide a fluid tight sealbetween catheter 18 and mounting block 20. As shown, the inflation lumen96 continues through mounting block 20 into an interior chamber 110formed in mounting block 20.

Referring to FIG. 3, as shown, chamber 110 is in fluid communicationwith an injection port 112. Self sealing septum 42 is preferably mountedonto injection port 112. Thus, any air to be aspirated out of catheter18 or any isotope to be injected into catheter 18 will be drawn throughinflation lumen 96, chamber 110 and injection port 112 by means of aneedle penetrating self sealing septum 42.

Referring now to FIG. 3C, a proximal end 114 of catheter 18 extends outa proximal end 116 of mounting block 20. Thus, mounting block 20additionally serves as a “handle” for manipulation of balloon catheter18 along a guide wire. As shown, a plurality of “O” rings 118 areprovided between proximal end 114 of catheter shaft 56 and an innersurface of proximal end 116 of mounting block 20 to provide a fluidtight seal.

Referring back to FIG. 3, aspiration syringe 16 is of known variety andgenerally includes a syringe body 120 having a plunger 122 slidablymounted therein. A syringe needle 124 extends from syringe body 120. Inutilizing balloon catheter 18 to deliver an isotope fluid to a selectedsite, it is necessary to avoid problems with irregular dosimetry byproviding a vacuum within balloon catheter 18. Thus, in order to prepareballoon catheter 18 for use, aspiration syringe 16 is advanced towardmounting block 20 such that syringe needle 124 pierces self sealingseptum 42 and enters chamber 110 of mounting block 20. Plunger 122 isdrawn to provide approximately a 60 cc vacuum on catheter 18 for about10 seconds. Upon removal of aspiration syringe 16 from mounting block20, self sealing septum 42 seals about itself thereby retaining thevacuum within the assembled balloon catheter 18 and mounting block 20.

Referring to FIG. 4, after an angioplasty procedure has been performed,the angioplasty dilatation balloon is removed from a patient leaving aguide wire 126 in place and extending down to the now expanded stenoticregion of a vessel V having compressed plaque P. A proximal end of guidewire 126 may be inserted into guide wire lumen 58 at distal end 52 ofballoon catheter 18 and balloon catheter 18 maneuvered to theconstricted site along guide wire 126. Once balloon catheter 18 has beenpositioned within a patient (FIG. 6.), fluid transfer device 22containing isotope I may be engaged with mounting block 20 in a mannerdescribed hereinabove (FIG. 5).

Referring to FIGS. 7 and 7A, upon engagement of fluid transfer device 22with mounting block 20, booted needle 68 of fluid transfer device 22engages self sealing septum 42 of mounting block 20. As shown, needle 70pierces self sealing septum 42 while elastomeric boot 72 expands toprovide an additional seal against self sealing septum 42. Inflationdevice 24 may then be affixed to transfer device 22 in a mannerdescribed hereinabove and activated to a known predetermined pressure todrive saline into saline chamber 76 thereby forcing piston 80 tocompress isotope I contained in isotope chamber 78 and force isotope Ithrough needle 70 into chamber 110. Isotope I forced through chamber 110is unimpeded by air due to the vacuum created within the inflationchamber 110 and isotope I is forced into inflation lumen 96.

Referring now to FIG. 8, as isotope I is forced through inflation lumen96, it passes through inflation ports 98 into an interior of balloon 54thereby expanding balloon 54 into contact with the compressed plaque Pand any other exposed vascular tissue V within the vascular system atthe operative site. As noted above, balloon 54 may be formed as anelastic or inelastic balloon. In either event, pressures are maintainedat sufficiently low levels such that balloon 54 does not perform anyfurther dilatation within the previously expanded region of the vascularsystem. The balloon 54 is maintained in an inflated condition withisotope I for an appropriate treatment time. Depending on the treatmenttime, it may be desirable to undertake repeated inflations anddeflations of balloon 54 with isotope I to allow a sufficient level ofperfusion to occur in between balloon inflations. Alternatively, it isalso contemplated that a balloon configuration utilized with the presentsystem may have varying provisions for perfusion of blood flow pastballoon 54. This may be accomplished by separate perfusion chambersextending through balloon 54 or altering the surface of balloon 54slightly to provide irregularities or minimal perfusion channelsextending along the length thereof to the extent that it would notcompromise uniform dosimetry of the surrounding tissue.

Referring now to FIG. 9, as noted above, pressure in inflation device 24is maintained at a predetermined level such that the pressure of theisotope fluid within balloon 54 does not exceed another known andpredetermined level. However, there is provided pressure relief valve 26which, when the pressure of saline exceeds a predetermined level, willallow seal 88 to compress spring 92 thereby allowing saline S to passthrough pressure relief valve 26 and be siphoned off through drain tube94. In this manner, over pressurization of balloon 54 may be avoided.

When the procedure is completed, device for radiation therapy 12 may beremoved to a shielded container or safe for safe deactivation,disassembly and disposal.

Referring now to FIGS. 10 and 10A, an alternative balloon catheter 130is provided for use with the above-described system. Balloon catheter130 is of “rapid exchange” style. Balloon catheter 130 generallyincludes a catheter shaft 132 having a balloon 134 mounted on a distalend 136 of catheter shaft 132. A guide wire lumen 138 extends from adistal port 140 formed in a distalmost end 142 of catheter shaft 134 andextends proximally beyond the length of the balloon to a proximal port144 formed proximally of balloon 134. It is also contemplated that theentire guide wire lumen including distal and proximal guide wire portsbe located entirely distal of balloon 134.

In order to form the relatively short guide wire lumen 138 extendingalong the length of balloon 134, a plug 146 is provided within guidewire lumen 138. Plug 146 defines a second lumen 148 which extends fromplug 146 proximally to a proximalmost end 150 of catheter shaft 132. Bycontinuing a lumen from plug 146 to the proximalmost end 152 of cathetershaft 132, lumen 148 is configured to receive a separate stiffeningmandrel which may be inserted into lumen 148 to facilitate insertion ofballoon catheter 18 along guide wire 126 as it is maneuvered through apatients vascular system.

Balloon catheter 130 is generally affixed to mounting block 20 in thesame manner as that of balloon catheter 18 described hereinabove.Specifically, a threaded cap 152 is configured to engage threads 104formed in a distal end 106 of mounting block 20.

It will be understood that various modifications may be made to thedisclosed embodiments. For example, various balloon configurations toprovide uniform irradiation of tissue may be provided. Alternatively,multiple balloons may be used. Further, mounting block 20 and transferdevice 22 may be modified to allow use thereof with standard knownballoon angioplasty catheters thereby allowing the balloon angioplastycatheter to remain in place as air is aspirated out of the catheter andisotope is subsequently injected into the balloon thereby reexpandingthe balloon into contact with surrounding tissue to provide uniformirradiation of the tissue. Additionally, alternative isotopes may beutilized depending upon the particular dosage required and half life ofthe isotope. Thus, the above description should not be construed aslimiting, but merely as exemplifications of preferred embodiments. Thoseskilled in the art will envision other modifications within the scopeand spirit of the claims appended hereto.

What is claimed is:
 1. A system for radiation therapy of a vesselcomprising: a transfer device defining a first chamber at a first endthereof and a second chamber at a second end thereof the transfer deviceincluding a piston movably disposed therein and separating the first andsecond chambers; a catheter engageable with the transfer device, thecatheter including an expandable portion and defining a lumen incommunication with the expandable portion; mounting structure operablyassociated with the catheter, wherein an interior of the mountingstructure is in communication with the lumen and the transfer device;and a radioactive substance located in one of the first and secondchambers of the transfer device and movable between the transfer deviceand the catheter in response to movement by the piston.
 2. A system asrecited in claim 1, further comprising a n inflation device removablyengageable with the transfer device.
 3. A system as recited in claim 1,further comprising an inflation device for providing a first fluid tothe first chamber, the inflation device being removably engageable withthe first end of the transfer device.
 4. A system as recited in claim 1,wherein the expandable portion includes an inflatable balloon.
 5. Asystem as recited in claim 4, wherein the lumen extends from the balloonto a location adjacent a proximal end of the catheter.
 6. A system asrecited in claim 1, wherein the mounting structure includes a fluidchamber in fluid communication with the lumen.
 7. A system as recited inclaim 1, wherein the radioactive substance is located in the secondchamber and movable between the second chamber and the expandableportion in response to movement of the piston.
 8. A system as recited inclaim 1, wherein the first chamber of the transfer device has a firstpredetermined cross-sectional area and the second chamber of thetransfer device has a second predetermined cross-sectional areadifferent from the first predetermined cross-sectional area.
 9. A systemas recited in claim 1, wherein the piston includes a first piston headmovably mounted within the first chamber and a second piston headmovably mounted within the second chamber.
 10. A system as recited inclaim 1, wherein the transfer device includes an injection needleextending from the second chamber.
 11. A system as recited in claim 10,wherein the injection needle is surrounded by an elastomeric boot.
 12. Asystem as recited in claim 10, wherein the transfer device has a needleshield extending from the second chamber to the second end of thetransfer device.
 13. A system as recited in claim 12, wherein the needleshield includes a bayonet mount engageable with a corresponding bayonetmount structure on the mounting structure.
 14. A system as recited inclaim 10, wherein the mounting structure is a mounting block having aself-sealing septum, the septum configured to seal about the injectionneedle.
 15. A system as recited in claim 14, wherein the mounting blockincludes a chamber in fluid communication with the lumen of thecatheter.
 16. A system as recited in claim 15, wherein the mountingblock has an injection port in fluid communication with the chamber, theseptum of the mounting block being mounted on the injection port.
 17. Asystem as recited in claim 14, wherein the mounting block is connectedto the second chamber of the transfer device with a proprietaryinterlock that is electronically coded with respect to the catheter sizeand function.
 18. A system as recited in claim 2, further comprising anover pressure relief valve mounted on the inflation device.
 19. A systemas recited in claim 1, wherein the radioactive substance includes a betaor gamma emitting radio isotope in liquid or gas form.
 20. A system asrecited in claim 1, wherein the catheter includes a guide wire lumenextending from a first guide wire port at a distal end of the catheterto a proximal guide wire port located proximal to the expandableportion.
 21. A system as recited in claim 20, wherein the proximal guidewire port is adjacent a proximal end of the catheter.
 22. A system asrecited in claim 3, wherein the first fluid is saline.
 23. A method ofirradiating vascular tissue comprising the steps of: providing a ballooncatheter, an inflation device and a transfer device, the transfer devicehaving a first chamber and a second chamber and a piston or membranetherein for separating the first and second chambers; drawing aradioactive substance into the second chamber of the transfer device;inserting the balloon catheter into a vascular system such that aballoon associated with the balloon catheter is positioned at a stenoticsite; attaching the balloon catheter to the transfer device such that aninflation lumen of the catheter is in fluid communication with thesecond chamber of the transfer device; connecting the inflation deviceto the transfer device such that the inflation device is in fluidcommunication with the first chamber of the transfer device; injectingfluid from the inflation device into the first chamber of the transferdevice to move the piston or membrane of the transfer device to forcethe radioactive substance out of the second chamber and into theinflation lumen to inflate the balloon.
 24. The method as recited inclaim 23, wherein the step of drawing a radioactive substance includesthe steps of: connecting the first chamber of the transfer device to theinflation device; bringing a source of the radioactive substance intofluid communication with the second chamber of the transfer device; andactuating the inflation device to apply negative pressure in the firstchamber thereby drawing the piston to create a negative pressure in thesecond chamber to draw the radioactive substance out of the source ofthe radioactive substance and into the second chamber.
 25. The method asrecited in claim 24, further comprising the step of disconnecting thetransfer device from the inflation device and the source of theradioactive substance.
 26. The method as recited in claim 23, furthercomprising the step of creating a vacuum in the balloon catheter and theinflation lumen prior to the step of inserting the balloon catheter intothe vascular system.
 27. The method as recited in claim 23, wherein thestep of attaching includes affixing a proximal end of the ballooncatheter to a mounting block and affixing the transfer device to themounting block such that of the transfer device is in fluidcommunication with the inflation lumen of the balloon catheter throughthe mounting block.
 28. The method as recited in claim 23, furthercomprising the step of providing adequate shielding for an operator anda patient, such shielding being incorporated into at least the ballooncatheter.
 29. A device for radiation therapy of a vascular systemcomprising: a transfer device defining a first chamber at a first endthereof and a second chamber adjacent the first chamber, the transferdevice including a piston or membrane movably disposed therein toseparate the first and second chambers; an inflation device containing afirst fluid transferable to the first chamber of the transfer device; acatheter having an inflatable balloon adjacent a distal end of thecatheter and defining an inflation lumen extending from the balloon to alocation adjacent a proximal end of the catheter; and a radioactivesubstance located in the second chamber of the transfer device andmovable between the second chamber and the balloon in response tomovement of the piston or membrane by actuation of the inflation device.30. The device as recited in claim 29, wherein the inflation device isremovably engageable with the first end of the transfer device.
 31. Thedevice as recited in claim 29, further comprising mounting structureremovably associated with the balloon catheter and having a fluidchamber in fluid communication with the inflation lumen, the mountingstructure being removably engageable with a second end of the transferdevice such that the fluid chamber of the mounting structure is in fluidcommunication with the second chamber of the transfer device.
 32. Adevice for radiation therapy of tissue comprising: a transfer devicedefining a first chamber and a second chamber adjacent the firstchamber, the transfer device including a partition disposed therein toseparate the first and second chambers, the partition being movablewithin the transfer device in response to a force exerted within thefirst chamber; a catheter having an inflatable balloon adjacent a distalend of the catheter and defining an inflation lumen extending from theballoon to a location adjacent a proximal end of the catheter; and aradioactive substance located in the second chamber of the transferdevice and movable between the second chamber and the balloon inresponse to movement of the partition.
 33. A device as recited in claim32 further comprising a forcing device for providing the force to movethe partition of the transfer device.
 34. A device as recited in claim33, wherein the forcing device is configured to provide substance to thefirst chamber of the transfer device.
 35. A device as recited in claim34, wherein the substance is fluid.
 36. A method of irradiating tissuecomprising the steps of: providing a transfer device and a ballooncatheter connected to the transfer device, the transfer device having afirst chamber and a second chamber and a movable partition therein forseparating the first and second chambers, an inflation lumen of thecatheter being in fluid communication with the second chamber of thetransfer device; providing a radioactive substance in the second chamberof the transfer device; inserting the balloon catheter into a body suchthat a balloon associated with the balloon catheter is positioned at atreatment site; and forcing a substance in the first chamber of thetransfer device to move the partition of the transfer device to therebyforce the radioactive substance out of the second chamber and into theinflation lumen to inflate the balloon.
 37. A method as recited in claim36, wherein the step of forcing is exerted by an inflation deviceconnected to the transfer device.
 38. A method as recited in claim 36,wherein the step of forcing is performed by forcing fluid in the firstchamber of the transfer device.